Introduction

Hypoxia-inducible factor (HIF)1α has been shown to be activated and induces a glycolytic shift under hypoxic condition, however, little attention was paid to the role of HIF1α-actuated fructolysis in hypoxia-induced heart injury.

Objectives

In this study, we aim to explore the molecular mechanisms of miR-155-mediated fructose metabolism in hypoxic cardiac fibroblasts (CFs).

Methods

Immunostaining, western blot and quantitative real-time reverse transcription PCR (qRT-PCR) were performed to detect the expression of glucose transporter 5 (GLUT5), ketohexokinase (KHK)-A and KHK-C in miR-155^−/− and miR-155^wt CFs under normoxia or hypoxia. A microarray analysis of circRNAs was performed to identify circHIF1α. Then CoIP, RIP and mass spectrometry analysis were performed and identified SKIV2L2 (MTR4) and transformer 2 alpha (TRA2A), a member of the transformer 2 homolog family. pAd-SKIV2L2 was administrated after coronary artery ligation to investigate whether SKIV2L2 can provide a protective effect on the infarcted heart.

Results

When both miR-155^−/− and miR-155^wt CFs were exposed to hypoxia for 24 h, these two cells exhibited an increased glycolysis and decreased glycogen synthesis, and the expression of KHK-A and KHK-C, the central fructose-metabolizing enzyme, was upregulated. Mechanistically, miR-155 deletion in CFs enhanced SKIV2L2 expression and its interaction with TRA2A, which suppresses the alternative splicing of HIF1α pre-mRNA to form circHIF1α, and then decreased circHIF1α contributed to the activation of fructose metabolism through increasing the production of the KHK-C isoform. Finally, exogenous delivery of SKIV2L2 reduced myocardial damage in the infarcted heart.

Conclusion

In this study, we demonstrated that miR-155 deletion facilitates the activation of fructose metabolism in hypoxic CFs through regulating alternative splicing of HIF1α pre-mRNA and thus circHIF1ɑ formation.

中文翻译：

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miR-155下调通过激活心脏成纤维细胞中的果糖代谢来保护心脏免受缺氧损伤

介绍

缺氧诱导因子 (HIF)1α 已被证明在缺氧条件下被激活并诱导糖酵解转变，然而，很少有人关注 HIF1α 驱动的果糖分解在缺氧诱导的心脏损伤中的作用。

目标

在这项研究中，我们旨在探索 miR-155 介导的缺氧心脏成纤维细胞 (CF) 中果糖代谢的分子机制。

方法

进行免疫染色、蛋白质印迹和定量实时逆转录 PCR (qRT-PCR) 以检测 miR-155 -/- 和 miR 中葡萄糖转运蛋白 5 (GLUT5)、酮糖糖激酶 (KHK)-A 和 KHK-C^的表达-155 ^wt CFs 在常氧或缺氧条件下。对 circRNA 进行微阵列分析以鉴定 circHIF1α。然后进行 CoIP、RIP 和质谱分析，并鉴定出 SKIV2L2 (MTR4) 和 transformer 2 alpha (TRA2A)，后者是 transformer 2 同系物家族的成员。pAd-SKIV2L2在冠状动脉结扎后给药，以研究SKIV2L2是否可以对梗死心脏提供保护作用。

结果

当 miR-155 ^-/-和 miR-155 ^wt CFs 暴露于缺氧 24 小时时，这两种细胞表现出糖酵解增加和糖原合成减少，以及中央果糖 KHK-A 和 KHK-C 的表达 -代谢酶，被上调。从机制上讲，CFs 中 miR-155 的缺失增强了 SKIV2L2 的表达及其与 TRA2A 的相互作用，从而抑制了 HIF1α 前体 mRNA 的可变剪接形成 circHIF1α，然后减少的 circHIF1α 通过增加 KHK- C 亚型。最后，SKIV2L2 的外源性递送减少了梗死心脏的心肌损伤。

结论

在这项研究中，我们证明了 miR-155 缺失通过调节 HIF1α 前体 mRNA 的可变剪接从而促进了缺氧 CFs 中果糖代谢的激活，从而促进了 circHIF1ɑ 的形成。